1. The Field of the Invention
The field of the invention relates to an improved machine visual inspection device and method which uses the technique of video scanning a workpiece to be inspected by video camera means which transmits signals from the video signal plate point or region array in the camera view or inspection field by line and time to a computer's central processing unit in which is stored a pre-scanned workpiece image in the format of a video array or reference field for comparison. The device is particularly useful in inspecting brushes of various kinds.
2. Description of the Prior Art
The prior art is best demonstrated by U.S. Pat. Nos. 3,872,243 (Mar. 18, 1975) to Soames, et. al.; 4,319,272 (Mar. 9, 1982) to Henry; 4,344,146 (Aug. 10, 1982) to Davis, et. al.; 4,417,274 (Nov. 22, 1983) to Henry; 4,521,807 (June 4, 1985) to Werson; 4,556,902 (Dec. 3, 1985) to Krufka and 4,589,140 (May 13, 1986) to Bishop, et. al. in which typical circuitry and protocol permit a workpiece to be inspected in a video scanned inspection field made up of discrete line and time addressable points or regions. The workpiece image being scanned receives a measured, defined light value or datum for each point or region in the field. A series of analogue signals are transmitted region, by region each in corporating a datum, in a defined order on a carrier to a digitizer. The addresses and data are then digitized and read into a central processing unit of a computer in which resides in memory a predetermined "correct" image having an identical type of light value for each address. A compare function resident in the central processing unit memory determines whether the transmitted image values and the stored image values match, or map and if they do not, within predefined parameters, a rejection means is activated. See also U.S. Pat. Nos. 3,902,811 (Sept. 2, 1975) to Altman, et. al.; 3,980,870 (Sept. 14, 1976) to Kawahara; 4,437,115 (Mar. 13, 1984) to Yoshida; 4,454,541 (June 12, 1984) to Suzuki, et. al.; 4,473,842 (Sept. 25, 1984) to Suzuki, et. al.; 4,479,145 (Oct. 23, 1984) to Azura, et. al.; 4,480,264 (Oct. 30, 1984) to Duschl; 4,492,476 (Jan. 8, 1985) to Miyazawa; 4,433,385 (Feb. 21, 1985) to DeGasperi; 4,576,48 (Mar. 18, 1986) to Pryor, and 4,606,635 (Aug. 19, 1986) to Miyazawa.
Reference is also made to FRGP/UM (Offeniegungs-schrift) Nos. DE3417086A1, DE3501512 and European Pat. No. 0189067 to Zahoransky which in general terms show partial solutions to problems involving the inspection of brushes by unspecified camera imaging techniques and by photocells. Mechanical sensors taught in the Zahoransky patent are not applicable here.
U.S. Pat. No. 4,246,606 (Jan. 20, 1981) to Yoshida, utilizes a white standard installed in the inspection field to assist in the standardization of brightness and U.S. Pat. No. 4,570,180 (Feb. 11, 1986) to Baier, et. al., utilizes a gray scale in the inspection field for certain purposes not germane to the present invention.
The prior art is not responsive to the inevitable error effects that the reflectance values of ambient light have on the inspection field image. These often fluctuate randomly or by local lighting changes and reflectance errors cause improper rejection (or acceptance). The inspection is also not responsive to alignment errors which are inherently induced in workpiece transfer systems. These cause mismatching or mapping and, therefore, improper rejection (or acceptance).